Conventional stereo imaging devices captured images by placing two cameras on the left and right as in human eyes, i.e., left and right images are captured by two cameras on the left and right to obtain left and right image data. The left and right image data is synthesized by every frame, every line or the like to obtain stereoscopic image data.
FIG. 16 is a schematic diagram showing an example of the configuration of essential parts of a conventional stereo imaging device.
In FIG. 16, a conventional stereo imaging device 100 is provided with two lens means 101 and 102 on the left and right, a solid-state imaging element 103 to which lights are collected by the lens means 101, and a solid-state imaging element 104 to which lights are collected by the lens means 102. A focal point is made in each imaging surface of the solid-state imaging elements 103 and 104 by the lens means 101 and 102 and image lights on the left and right are separately imaged by the solid-state imaging elements 103 and 104. The lens means 101 and 102 are expressed as single simplified convex lenses. Although a lens means may be a single convex lens, a lens means generally consists of a combination of a plurality of lenses.
For example, the Sharp smartphone SH-12C that went on sale in 2011, which is described in Non-Patent Literature 1, constitutes a stereo imaging device equipped with two independent cameras on the left and right. The smartphone is capable of expressing three-dimensionality by displaying stereo images that are simultaneously captured with the two independent cameras on the left and right on a parallax barrier 3D display.
In the aforementioned conventional stereo imaging devices, there is an issue of not being able to accurately fix the positional relationship of left and right images due to the two cameras being independent. If the positional relationship of left and right images cannot be accurately fixed, an accurate three-dimensional image cannot be obtained because the distance to a subject cannot be accurately obtained. In this regard, a means for correcting tilts and positional deviations from a stereo image has been proposed, for example, in Patent Literature 1. A correction is made by trimming so that a portion without parallax would be at the same position in left and right images.
Further, a means for stereo capturing with a single camera as in Patent Literature 2 has been proposed as a means that do not require such a correction. In Patent Literature 2, an imaging region is largely divided into two regions and pixels for receiving lights with different directionality from each other are disposed to obtain an image with different parallax.
Patent literature 2 is explained in further detail by using FIG. 17.
FIG. 17 is a cross-sectional view showing an example of a configuration of a conventional imaging section disclosed in Patent Literature 2 in detail.
In FIG. 17, a conventional imaging section 100 is utilized in a distance measuring device. An incident light L1 from a lens 101 is decomposed into two luminous fluxes L11 and L12 with an equal incident angle property by a beam splitter 102. The two luminous fluxes L11 and L12 are imaged with imaging elements 103R and 103L for right and left eyes, respectively.
In the imaging elements 103R and 103L, the direction of incident angle with the maximum sensitivity is set to a direction that deviates from a direction that is directly in front of an imaging surface, and the deviated directions are set in different directions. From the above setting, each of the imaging elements 103R and 103L is set to have directivity with a characteristic of deviating from the direction that is directly in front of an imaging surface to form different directivity properties. The imaging section 100 outputs imaging results by the imaging elements 103R and 103L as imaging signals SR and SL for right and left eyes.
From the above, an incident light from an optical system is separated into two luminous fluxes with equal incident angle characteristic, and each luminous flux is then imaged by the imaging elements 103R and 103L for right and left eyes, respectively, to obtain imaging results for right and left eyes having parallax. Thus, to that extent, the configuration of an optical system is simplified in addition to having a reduced size in comparison to a case of generating two luminous fluxes having parallax with an optical system.
The imaging elements 103R and 103L for right and left eyes are, for example, CCD solid-state imaging elements. The imaging elements are made by forming photosensors 105 in a matrix pattern and a register for sequentially transferring and outputting electrical charges accumulated by the photosensors 105 on a semiconductor substrate 104 and forming a color filter and on-chip microlens 106 on a surface. The imaging elements 103R and 103L are set so that a direction of an incidence angle with a maximum sensitivity is a direction deviated from a direction that is directly in front of an imaging surface with the setting of an incident pupil by the on-chip microlens 106.
Specifically, the imaging element 103R for a right eye is made so that the on-chip microlens 106 is deviated by only a predetermined interval TR in a transverse direction with respect to the photosensor 105. Further, the imaging element 103L for a left eye is made so that the on-chip microlens 106 is deviated by only a predetermined interval TR in the opposite direction from that for the imaging element 103R with respect to the photosensor 105.
From the above, the imaging elements 103R and 103L for right and left eyes selectively allow entry and receive a light from an incoming direction related to right and left eyes from two luminous fluxes L11 and L12 that are separated by the beam splitter 102 to output image results for right and left eyes having parallax, respectively.